Signaling loop including unbroken railroad track



Aug. 20, 1968 v F. L. HATKE EITAL SIGNALING LOOP INCLUDING UNBROKEN RAILROAD TRACK Filed March 19, 1965 I VL'I L9 1Q {8 o 'F?// "N j 11 16 1 5 Nil/CHIC! 2 (7/44 65 Madam e: Z1, (WI/V66 INVENTORS 6:02 II. 600 6 F250 1. H474:

sob-veal 9km United States Patent 3,398,275 SIGNALING LOOP INCLUDING UNBROKEN RAILROAD TRACK Fred L. Hatke, Skillman, and George W. Gray, Lambertville, N..I., assignors to Radio Corporation of America, a corporation of Delaware Filed Mar. 19, 1965, Ser. No. 441,089 1 Claim. (Cl. 246-34) This invention relates to apparatus for the detection and control of and communication to a vehicle which runs on conductive tracks and particularly to signaling loops comprising a part of the conductive tracks.

When using the inductive type of train detection, it has been suggested to provide a wire loop between or beneath the railroad tracks, so that when a railroad vehicle runs over the loop the inductance thereof decreases. Such loops however have the disadvantage of being subject to mechanical damage by the train passing over the tracks or by a flame thrower used to clear snow, ice and Weeds. Furthermore, since the rails are electrically coupled to such loops, at least one insulated joint must be provided in the tracks near the loop to prevent a distant train from varying the inductance of the loop, thereby giving a false indication. In many cases an insulated joint in each rail may be necessary to prevent such false indication.

It is an object of this invention to provide an improved loop suitable for detection of railroad vehicles passing over a track.

It is another object of this invention to provide an improved detection or signaling loop for a railroad requiring no substantial modification or adaptation of existent rail track.

According to the invention, connectors are provided between the rails and running perpendicular thereto at spaced points along the rails to provide two short circuits therebetween. The connection of suitable measuring or other signaling equipment to the loop so formed can be made by connecting each of two leads to the respective rails at a point substantially halfway between the connections across the tracks. In another embodiment of this invention, the leads are connected to the rails at points closer to one connector than the other whereby the loop is given a directional characteristic. Since the only adaptation of the tracks that is necessary to provide the loop is the provision of the connection between the tracks and the connecting of the leads from measuring or other equipment to the rails of the track, no substantial modification of an existing set of rails is required to provide the loop. Since the only apparatus added to the rails to provide a structure additional to the tracks, which is subject to damage and which needs maintenance, is provided than with prior art railroad loops.

The novel features of the invention both as to its organization and method of assembly, as well as additional objects and advantages thereof will be understood more readily from the following description when read in conjunction with the accompanying drawing in which FIGURE 1 is a diagrammatic showing of the loop of this invention,

FIGURE 2 is a sectional view of FIGURE 1 along line 22 thereof.

FIGURE 3 is a diagrammatic showing of a modified loop of this invention.

A connector is provided for connecting the two rails 12, 12 and extending substantially perpendicularly thereto. The connector 10 comprises a stranded conductor and conductive plugs 16 connected to the ends of the stranded conductor. These plugs may be forced into holes 18 in the rails 12 as by driving them with a hammer, to make connections between the connector 10 and the rails 12. At a predetermined distance from the first connector 10,

another similar connector 10 is provided between the rails 12, completing the loop 19. The connectors 10 may lie below the surface of the ties (not shown) on which the rails are laid.

Input connections to and output connections from the loop are provided by leads 20, one connection to each rail 12, at the point thereof substantially midway between the connectors 10. The leads 20 can also be connected to the rails 12 by means of conductive plugs 16 connected to the ends of the leads 20. These last named plugs 16 extend through holes 18 into the webs of the rails 12, 12. The leads 20, 20 are shown as connected to a utilization device which can be a means to measure inductance 21, in case the loop is used for vehicle detection, or to a source of signaling current or a receiver or both (not shown), in case the loop is used for signaling.

In explanation of the operation of the described loop 19, let it be assumed that a railroad vehicle (not shown) including a conductive wheel and axle assembly 24 is on the rails 12, 12 approaching the loop 19 but on one side of both of the connectors 10, 10. This assembly 24 will then provide a connection between the rails 12, 12 and also a mass of conductor outside of the loop 19. The connection between the rails 12, 12 provided by the connectors 10, 10 will prevent the wheel assembly 24, while outside the loop 19, from having any substantial effect on the inductance thereof. As soon as the wheel assembly 24 moves onto the rails between the connectors 10, 10, the size of the loop 19 is decreased by the connection across the rails 12, 12 provided by the wheel assembly 24, decreasing the inductance of the loop 19. Also, the presence of the conductive mass of the wheel assembly, or of other metal portions of the railroad vehicle in the area of the loop 19 decreases the inductance thereof. Since the inductance of the loop 19 is decreased by either the connection between the rails provided by the wheel assembly 24 or by the etfect of the conductive mass in the area of the loop, the described loop 19 will detect the presence of a railroad vehicle within the loop area whether the wheel assembly 24 makes good contact between the rails or not.

The inductance change caused by a railroad vehicle passing over the loop 19 can be detected by the inductance change detector 21. The detector 21 can comprise a portion of a tuned circuit whereby the phase of a given wave applied to this tuned circuit is varied by changes in the inductance of the loop 19. The phase changed wave is compared to a given wave whose phase is not changed to detect the presence of a vehicle in the loop 19.

If the loop 19 is to be used for communication, a transmitter and receiver can be substituted for the inductance change detector 21. Another loop (not shown) is then carried on each railroad vehicle with which communication may be desired, and this other loop may itself be connected to a transmitter and receiver on the vehicle. The loop on the rail vehicle and the railroad loop 19 will be coupled when the vehicle passes close to the railroad loop 19 whereby communication with a moving railroad vehicle is made possible.

The connections of the leads 20, 20 to the rails 12, 12 are shown in FIGURE 1 as being substantially halfway between the connectors 10 therebetween. However, the connections of the leads 20', 20' to the rails 12, 12 may be made closer to one connector 10 than the other connector 10 as shown in FIGURE 3, whereby the section of the loop 19' between the connections of the leads 20', 20 and the left hand connector 10 (as viewed in FIG. 3) is smaller than the right hand section of the loop 19. This connection of the leads 20, 20' to the rails 12, 12 presents the advantage that the smaller section of the loop 19' is more sensitive to vehicles passing thereover than the larger section, whereby the direction of travel of the vehicle may be determined by the response of the 3 loop 19 of FIGURE 3 to the passage of vehicles thereover.

The loops 19 and 19' herein described require sub stantially no modification and only minor adaptation of the rails and include less structure in addition to the track that is subject to damage and that needs maintenance than prior art loops used with rails.

Although only a single loop structure has been shown and described, variations are possible within the spirit of the present invention. For example, any type of conductor or any means of making electrical connection between the ends of the conductors and a track may be used instead of the connectors 16 and their plugs 18. Hence it should be understood that the foregoing description is to be considered as illustrative and not in a limiting sense.

What is claimed is:

1. A signaling and vehicle detecting loop system comprising a pair of rails,

a pair of spaced connectors connecting said rails and extending substantially perpendicularly thereto,

a utilization device having terminals, and

a pair of leads, each lead being connected between a point on a respective rail that is between said pair of spaced connections and that is closer to one of said connectors than to the other thereof and a respective terminal of said utilization device.

References Cited UNITED STATES PATENTS OTHER REFERENCES Doble, Presence Detectors Can Aid Track Circuits, Railway Signaling and Communications (RSC), June,

20 1963, pp. 30-32 and 34.

ARTHUR L. LA POINT, Primary Examiner.

S. T. KRAWCZEWICZ, Assistant Eraminer. 

1. A SIGNALING AND VEHICLE DETECTING LOOP SYSTEM COMPRISING A PAIR OF RAILS, A PAIR OF SPACED CONNECTORS CONNECTING SAID RAILS AND EXTENDING SUBSTANTIALLY PERPENDICULARLY THERETO, A UTILIZATION DEVICE HAVING TERMINALS, AND A PAIR OF LEADS, EACH LEAD BEING CONNECTED BETWEEN A POINT ON A RESPECTIVE RAIL THAT IS BETWEEN SAID PAIR OF SPACED CONNECTIONS AND THAT IS CLOSER TO ONE OF SAID CONNECTORS THAN TO THE OTHER THEREOF AND A RESPECTIVE TERMINAL OF SAID UTILIZATION DEVICE. 